Composite Trials in middle aged adults indicate that weight loss can be achieved and sustained with frequent contact over a long period of time, frequent self-monitoring, social support and motivational counseling. However, it is unclear whether this strategy would work in younger adults. Based on life stage, cultural context, environmental circumstances, and marketing pressures, behavioral Intervention may need to be substantially modified to be effective in young adults. Even more adaptation will be required for intervention to be effective in young adults from racial/ethnic minority groups. The proposed intervention builds on prior evidence with innovations directed at increasing effectiveness in young adults. Using cell phones to deliver a weight control intervention in this age group has the potential to be engaging, enjoyable, practical, cost-effective, sustainable, and broadly disseminated. We propose a trial in which a highly innovative but more risky intervention based almost entirely on use of cell phone technology and a second more incremental innovation over traditional behavioral intervention are each compared to a usual care control group. We will recruit a diverse target population of ovenweight/obese, generally healthy young adults, comprising approximately 35% non-Latino Whites, 35% non-Latino Blacks, and 30% Latinos, to be randomized to: 1) Usual care control: Educational materials and information but no behavioral intervention; 2) Cell-phone intervention: similar education and knowledge as the control group, but thereafter a behavioral intervention will be delivered almost exclusively via cell phone, particularly using the self-monitoring and social networking features of this technology; 3) Personal contact with cell-phone enhancement: personal contact intervention enhanced by cell-phone for self-monitoring. The post-randomization intervention period will last 24 months. The primary outcome is change in weight 12 months post-randomization; an important secondary outcome is weight change at 24 months. The formative phase will focus largely on technology/intervention development. RELEVANCE (See instructions): The obesity epidemic is affecting young adults, leading to increased risk of diabetes, high blood pressure, and cardiovascular disease. Based on life stage, cultural context, environmental circumstances, and marketing pressures, behavioral intervention may need to be substantially modified to be effective in young adults, espcially young minorities. Using cell phones to deliver a weight control intervention has the potential to be engaging, enjoyable, practical, cost-effective, (End of Abstract)